Spring Framework Interview Questions

Can you explain the core concepts of the Spring Framework?

The core concepts of the Spring Framework include Inversion of Control (IoC), Dependency Injection (DI), and Aspect Oriented Programming (AOP).

1. IoC involves a third-party object controlling the instantiation and creation of other objects rather than the objects creating or selecting themselves.
2. DI is a form of IoC where a third-party object injects object dependencies.
3. AOP involves adding additional behavior to existing code without modifying it, often for purposes such as logging and security.

How does Spring support the principle of loose coupling?

The Spring Framework promotes loose coupling through DI, which decouples object creation and usage. This allows for more flexibility in the code and easier maintenance and testing. Additionally, Spring supports dependency interfaces rather than concrete implementations, further promoting loose coupling.

Can you give an example of AOP in action with the Spring Framework?

One example of AOP in action with the Spring Framework is using Spring AOP to add transaction management to methods without explicitly adding transaction management code within the method itself. It allows for cleaner and more modular code. Another example could be using AOP to add logging functionality to specific methods without logging code within the method itself.

Can you explain the difference between a BeanFactory and ApplicationContext in Spring?

Both BeanFactory and ApplicationContext are responsible for instantiating, configuring, and managing beans. However, ApplicationContext also supports internationalization (i18n) and integrates with Spring technologies such as AOP and Spring MVC.

Additionally, ApplicationContext provides easier access to the bean configuration file information, while BeanFactory requires more manual handling of this information.

Can you give an example of how you would use primary and qualifier annotations with Autowiring in Spring?

If there are multiple beans of the same type, qualifiers can be used to specify which exact bean should be injected. This can be done through annotations such as @Qualifier on the field being @Autowired, or through using the qualifier attribute in XML configuration.

Furthermore, primary annotations can be used to specify a preferred bean among multiple candidates when no specific bean is specified through qualifiers. This can be done through the use of the @Primary annotation on a bean or through the primary attribute in XML configuration.

How do you configure Spring Security?

Spring Security can be configured through either Java or XML configuration. This includes configuring web security, setting up authentication and authorization, specifying protected resources, and setting up password encoding.

Additionally, Spring Security can be further customized through filters, authentication providers, and access decision managers.

Can you explain how Spring Boot simplifies Spring development?

Spring Boot simplifies Spring development by providing an easy way to set up and configure a project with common dependencies through the use of starters and auto-configuration.

Spring Boot also provides embedded servers, improved health checks and monitoring, and production-ready features. This allows for a quicker development process and a more efficient production application.

Can you give an example of using Spring Data JPA?

Spring Data JPA allows for the implementation of JPA repositories, which provide a way to access and manage data while also handling the underlying database communication.

To use Spring Data JPA, we can create a repository interface that extends JpaRepository. This interface can then be used to perform common operations on the data, such as finding entities by id or saving entities.

Additionally, we can also add custom methods and query creation to the repository interface for more specific database operations.

How does Spring MVC work?

Spring MVC follows the Model-View-Controller design pattern, where the controller handles requests and responses, the model represents the data, and the view is responsible for presenting the data to the client.

In Spring MVC, components such as controllers and views are typically configured through annotations. The DispatcherServlet acts as the front controller, handling all incoming requests and delegating them to the appropriate controller.

The controller then interacts with the model and chooses a view to be rendered for the response. This process is often referred to as the "request handling cycle."

Can you explain the role of a RestController in Spring MVC?

A RestController, also known as a RESTful web service controller, is responsible for handling RESTful web service requests. These controllers typically use annotations such as @RequestMapping to specify the mapping of specific URLs to their corresponding methods.

RestControllers also often use annotations such as @PathVariable and @RequestBody to access variables in the request URL or the request body.